In modern packaging printing industry, plastic is popular in many fields such as lamination or packaging materials to protect or demonstrate the goods. Here we would like to introduce the roles of plastics in packaging printing industry in two parts..
Plastic describes the ability of a material to be molded or formed. Historically this referred to natural materials such as was, clay, tar, rosin and asphalt. With advances in chemistry, the term plastic began to describe modified natural resins and finally a large group of synthetic materials that could be formed into useful shapes. The words plastic and polymer are used interchangeably, but plastic tends to be used to describe finished parts, polymer tends to describe the raw materials and is used by scientific community. Now plastic is used instead of polymer to indicate a specific category of high molecular weight materials which can he shaped using a combination of heat, pressure, and time. All plastics are polymers, but not all polymers are plastics. We will discuss those plastics and plastics structures that are useful as packaging materials. The concrete time of many different plastics began to be used and each plastic type has a unique structure and proper chemical name. However, chemical names can be lengthy and common industry usage is a mixture of trade names, common names and abbreviations. Spellings and abbreviations developed randomly, and today the same polymer may be spelled and abbreviated in a number different ways..
Packaging printing started with natural materials such as leaves. From there, it progressed to fabricated materials such as woven containers and pottery. Glass and wood have been used in packaging for about 5000 years. In 1823, Durand in England patented the canister, the first tin-plate metal container. The double seamed three-piece can ways in use by 1900. Paper and paperboard became important packaging materials around 1900. As soon as plastic materials were discovered, they were tried as packaging materials, mainly to replace paper packaging. Use of cellophane, which is a polymer but not truly a plastic, predated much of the use of plastics
The use of plastics in packaging printing applications began, for the most part, after World War II, polyethylene had been produced in large quantities during the war years, and it became commercially available immediately after the war. It was soon found that it could be formed easily into various shapes useful for packaging printing. An early application was in bread bags, replacing waxed paper. Polyethylene coatings replaced was in heat-sealable paperboard. It was also combined with paper as a coating to replace waxed paper and cellophane. The driving force behind the expansion of polyethylene use was to obtain a re-sealable package as well as transparent materials that allowed the product to be visible. Polyethylene remains the leading packaging plastic because of its low raw material prices, versatile properties, and its ease of manufacture and fabrication.
The growth of plastics packaging has accelerated rapidly since the 1970s, in large part because of one of the main features of plastics-low density, this low density made the use of plastics attractive because of the weight savings, which translates into energy savings for transportation of packaged goods. In addition, plastic packages are usually thinner than their counterparts in glass, metal, paper, or paperboard. Therefore, conversion to plastic packaging often permits economies of space as well as of weight. Saving in the amount of distribution packaging needed may also result; another important property is relatively low melting temperatures of plastics compared to glass and metals. Lower melting temperature mean less energy is required to produce and fabricate the materials and packages. While use of plastics in all applications has grown rapidly during this period, the growth in packaging has outpaced the growth in other sectors.
Many of the early applications of plastics were in food packaging. The substitution of plastics films for paper in flexible packaging led to the development of many new combinations of materials, and to the use of several polymers together to gain the benefit of there various attributes. The development of flexible packaging for foods picked up speed in the later 1940s and 1950s as the prepared foods business begin to emerge. Milk cartons using polyethylene coated paperboard were introduced in the 1905s. Here the driving force was economics: glass is more expensive in a systems sense, breakage of glass on line requires extensive cleaning, and objects into an otherwise clean environment.
In industrial packaging printing, plastics were used early as a part of multiwall shipping sacks that replaced bulk shipments, drums, and burlap sacks. Again, polyethylene film was the predominant materials used. Cement in 110kg bags became a major application of polyethylene film in the industrial sector. The polyethylene liner protects the cement from moisture that would cause it to solidify. Another large use of plastics in industrial packaging is as cushioning to protect goods from vibration and impact during shipping. Polystyrene, polyurethane and polyethylene foams are all used as cushioning, competing against paper-based cushioning materials.
Medical packaging printing has been another big user of plastics. As converting techniques improved, so that accurate molding of small vials could be accomplished at low cost, and as new polymers became available with the necessary characteristics, plastics have been substituted for glass in many applications. As medical procedures became more complex, more disposable kits were introduced, designed to have complete sets of equipments for specific procedures. These kits require special packaging printing to keep the parts organized and easily usable. It was here that thermoformed trays became standard, so that kit of pre-sterilized, disposable instruments and supplies, in the proper varieties and amounts, can be readily assembled. The plastic packaging printing allows the sterilization, as long as the package remains intact. Sterilization with ethylene oxide is facilitated by the use spun-bonded polymeric fabrics. Radiation sterilization depends on the use of polymers that retain their integrity after exposure to ionizing radiation.
The energy crisis in the 1970s, while at first leading to attacks on plastics as users of precious petroleum, actually accelerated the movement to packaging because of the weight reduction possible. Many metal cans and glass bottle s were replaced by plastic cans and bottles, and in many cases changes in packaging printing design moved the product out of rigid packaging altogether, into flexible packaging, which more often than not was made of plastic, Similarly, some metal drums were replaced by plastic drums. A major driving force was to reduce the fuel used for transportation of both packages and packaged goods by reducing the weight of the package. One important example is the introduction of the plastic beverage bottles.
Environmental concerns of the 1980s and early 1990s, caused by littering issues and a perceived lack of landfill space, caused a major rethinking of plastics package in use. Companies that used plastics had to defend the uses that were in place, and justify new application. The result was a more responsible approach to packaging printing in general, by most companies. As politicians and the public became more informed about the truth concerning plastics and the environment, the issues receded from the forefront, though recent concerns about the use of plastics bottles for beer illustrate that they have not disappeared altogether. Today, plastics packaging has earned its position as one of the choices of package designer. Decisions about which materials should be used require consideration of four factors: product requirements, market image, cost and environment issues.
